The great miracle of Christianity is that there is a fundamental change that occurs when we come to faith in Christ. There are two changes that happen to a believer that are both judicial (dealing with the problem of the guilt of our sin) and practical (dealing with the problem of our power over sin in our daily life.
Every problem in our lives and in our world is a result of man's rebellion against the One who made Him. Since Adam’s sin in the Garden, every man has been sinful and separated from God at their birth. We are sinners and we have sinned continually. And the penalty for sin is always separation from God. (see Romans 6:23). This separation makes us incapable of living as we were designed to live.